IEC 60942-2003 pdf – Electroacoustics – Sound calibrators

IEC 60942-2003 pdf – Electroacoustics – Sound calibrators.
5 Requirements 5.1 General 5.1.1 A sound calibrator conforming to the requirements of this standard shall have the characteristics described in this clause. Adaptors may be provided to accommodate more than one model of microphone. For the purpose of this standard, any such adaptor is an integral part of the sound calibrator. 5.1.2 The sound calibrator shall conform to the requirements of this standard for one or more of the sound pressure level and frequency combinations available. All the combinations conforming to the requirements given in this standard shall conform to the same class designation. Conformance to the requirements of this standard shall not be stated for sound pressure level and frequency settings for which this standard provides no tolerance limits. 5.1.3 Class LS sound calibrators shall be supplied with an individual calibration chart containing the information required by 6.2. For class 1 and class 2 sound calibrators, the specified sound pressure level(s) and specified frequency(ies) shall be given in the instruction manual. 5.1.4 Class LS and class 1 sound calibrators that require corrections for the influence of static pressure to conform to the specifications for the appropriate class shall have the letter ‘C’ added to their class designation. Class LS and class 1 sound calibrators shall not require corrections for any of the other environmental conditions to achieve the requirements specified for the appropriate class. Class 2 sound calibrators that require corrections for any of the environmental conditions to conform to the specified requirements shall have the letter ‘C’ added to their class designation. Where appropriate, the class designation shall be described as class LS/C, class 1/C, class 2/C. Where corrections are permitted, and are necessary to conform to the specified requirements as an environmental condition varies, these corrections shall be stated in the instruction manual.
5.1.5 Class 1 sound calibrators that require a correction for the influence of static pressure to conform to the specifications of this standard shall be supplied with a barometer. The barometer shall enable the static pressure to be measured so that the ability of a sound calibrator to conform to the requirements for the class is not affected. Class 2 sound calibrators that require a correction for the influence of static pressure to conform to the specifications of this standard shall be supplied with a barometer (which shall enable the static pressure to be measured in such a way that the ability of a sound calibrator to conform to the requirements for the class is not affected), unless the corrections are sufficiently small that for any change in static pressure of ±6,0 kPa the uncorrected measured sound pressure levels conform to the specifications of this standard. In this case, the corrections to be applied for the influence of variations in static pressure shall be stated in the instruction manual, together with information on how to calculate the relevant correction when operating the sound calibrator at different heights above sea-level.
5.1.6 Where a class 2 sound calibrator, that requires a correction for the influence of temperature or relative humidity to conform to the specifications of this standard, is supplied with the means to measure the relevant environmental condition, the supplied means shall enable the condition to be measured in such a way that the ability of a sound calibrator to conform to the requirements for the class is not affected. NOTE The ‘supplied means’ may provide the data directly in the form to be used to correct measured sound pressure levels to the reference environmental conditions. 5.1.7 The design of the sound calibrator and the materials used in the construction should be such as to provide long-term stability for the operation of the sound calibrator. 5.1.8 If a specific orientation of the sound calibrator is to be used to conform to the requirements of this standard, this orientation shall either be indicated on the sound calibrator, or the indication on the sound calibrator shall refer to the instruction manual, which shall state the required orientation. 5.1.9 All performance requirements relate to the operation of the sound calibrator following stabilizing of the coupling of the microphone and sound calibrator, and after the sound pressure level and frequency have stabilized. The elapsed time necessary for stabilization of the sound pressure level and frequency, which begins once the sound calibrator is switched on with the microphone coupled to it, shall be stated in the instruction manual, and shall not exceed 30 s for any applicable combination of environmental conditions specified in 5.4. The sound calibrator and microphone shall be allowed to reach equilibrium with the prevailing environmental conditions before coupling.